JP2835517B2 - Uninterruptible power system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply having an energized circuit switching AC switch only in a commercial direct feed circuit. FIG. 1 is a block diagram of a conventional uninterruptible power supply. In the figure, 1 is a commercial input terminal, 2 is an output terminal, 4 is a power failure detection and synchronization circuit, 5 is an AC switch switching circuit for switching a current supply circuit, 7 is a conversion circuit section of an inverter, 8 is a battery, and 9 is a battery charging circuit. Reference numerals 3 and 3 'denote a control circuit for the AC switches 6 on the commercial side and the inverter side, respectively, of the energizing circuit switching AC switches. Usually ACSW3
Is turned on and FCSW3 'is turned off to supply commercial direct feed. 9 is maintaining and charging 8 and 7 is in a standby state until an operation command signal from 6 is received. When the commercial input from 1 becomes a power failure, 4 detects the power failure and immediately turns off 3 and turns on 3 'via the AC switch switching circuit of 5. At the same time, through 6, the device 7 is driven to start battery power supply. When the power outage recovers, 4 detects power outage recovery. The synchronization circuit, which is another function of 4, works and sends a signal 6 so that the driving frequency of 7 is synchronized with the commercial frequency, and after the synchronization is completed, 5 turns on 3 and 3 'turns off and 6 turns 7 The transmission of the drive signal is stopped. In this way, the conventional standby type uninterruptible power supply secures the uninterruptible power supply for 2. Such a conventional device requires two (3, 3 ') AC switches for switching the energizing circuit. This is to prevent the cross current from flowing into the inverter conversion circuit by turning off the operation circuit of 7 and then restoring the direct feed circuit, or
There is a safety problem such that the commercial AC voltage is not applied to the inverter circuit by turning off the AC switch 3 '. In general, the AC switches 3 and 3 'are often semiconductor switches, which are expensive and complicated. FIG. 2 shows an embodiment of the present invention, and FIG. 3 shows only a main circuit portion thereof. In FIG. 2, 1 is a commercial input terminal, 2 is an output terminal, 4 is a power failure detection and synchronization circuit, 5 is an AC switch switching circuit for switching a conducting circuit, 7 is a conversion circuit section of an inverter, 8 is a battery, and 9 is a battery charging. The circuit 3 is an AC switch for switching the energized circuit, and 6 is a control circuit for the inverter conversion circuit. Normally, when commercial power is supplied to the input terminal 1, 3 is on, 7 is in a standby state until an operation signal from 6 is received, 9 is in direct commercial power supply while maintaining and charging 8.
When a power failure occurs, the power failure signal from 4 turns off 3 via 5. At the same time, drive 7 through 6, and 8
Power on battery. On the other hand, when the power outage recovers, 4 detects the power outage recovery. The synchronizing circuit, which is another function of 4, works and sends a signal to 6 so that the drive frequency of 7 is synchronized with the commercial frequency. After the synchronization is completed, the operation of 7 is stopped and 3 is turned off. In this way, an uninterruptible output is secured at the output terminal 2. The above operation will be described with reference to the main circuit operation shown in FIG. In FIG. 3, 1 is a commercial input terminal, 2 is an output terminal,
ACSWO is an AC switch for switching an energizing circuit, SW1 and SW2 are semiconductor switches of a push-pull type inverter circuit, T is a transformer for voltage conversion, 8 is a battery, and 9 is a battery charging circuit. In this circuit, during commercial direct delivery, ACSWO is on and SW1 and SW2 are off. If the winding ratio of the transformer T is appropriately selected so that the peak voltage on the primary side (P) of the transformer T does not exceed the battery voltage E at the time of direct commercial delivery, it is provided in parallel with each of SW1 and SW2. The overcharge of the battery is not performed by the reverse diode which is not used. Therefore, the secondary side (S) of the transformer T can be directly connected to the output terminal 2. FIG. 4 is an operation waveform diagram of each part of the device of the present invention, showing an operation example at the time of power failure and restoration of the input voltage VIN, the output voltage VOUT, and the inverter output current IO. As is clear from the above description, according to the present invention, only one AC switch for switching the energized circuit is required, and the cost is reduced. In addition, since the commercial voltage is applied to the transformer T during direct commercial delivery, if the winding of the rectifier for the charging circuit is wound around the transformer T, the utilization factor of the transformer increases, and the insulation of the charging circuit can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a conventional apparatus, FIG. 2, FIG. 3, and FIG. 4 are a block diagram, an essential part circuit diagram, and an operation waveform diagram of each part showing an embodiment of the present invention. . In the figure, 1 is a commercial input terminal, 2 is an output terminal, 3, 3 ', ACSWO is an AC switch, 4
Is a power failure detection circuit, 5 is an AC switch switching circuit, 6 is a control circuit, 7 is a converter circuit section of an inverter, 8 is a battery, 9 is a battery charging circuit, T is a transformer, and P and S are primary and secondary sides thereof. The coils, SW ₁ and SW ₂ are transistors.

Claims (1)

(57) [Claims] A converter 7 for converting the voltage of the battery 8 into an alternating current through a battery charging circuit 9, a battery 8, and switching elements SW1 and SW2 and a transformer T in which diodes are connected in parallel in the reverse direction; 7. An uninterruptible power supply comprising an inverter circuit comprising a control circuit 6 and an energization changeover switch (AC switch) 3 provided in a commercial direct feed circuit, wherein the AC output of the conversion unit 7 is supplied to the uninterruptible power supply. And the winding ratio of the primary side P and the secondary side S of the transformer T so that the voltage of the primary side P of the transformer T does not exceed the voltage of the battery 8. An uninterruptible power supply characterized by the settings.